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Tlie ash of the crude citrate is usually grey owing to the presence of ferric
oxide and contains alumina, silica and alkalies ; magnesium and aluminium,
when present, should be in very small proportions. These two metals come from
impure lime used in the manufacture of the citrate and lower the yield of the
latter appreciably. Further, sulphates, phosphates and oxalates should occur
only in minimal proportions.

In the steam-oven, crude citrates lose 4-6% of their weight. The pure
citrate loses 4-73% at 100°.

CSa = 76

A colourless or yellowish liquid, of ethereal odour if highly pure but
usually of repulsive smell owing to the presence of traces of organic sulphur
compounds. It is very readily inflammable, D — 1-272, 46-47°,
insoluble in water. The commonest impurity is sulphur, and it may contain
also hydrogen sulphide, sulphurous and sulphuric acids. The principal
tests are as follows.

1.  Sulphur.-.......5 c.c., allowed to evaporate spontaneously in a tared

glass dish, should leave no weighable residue ;   or about 2 c.c. is shaken
with a drop of dry, clean mercury, and note mack; if this becomes covered
with a brown, powdery layer.

2.  Hydrogen Sulphide.—The; liquid is shaken with u little lead car-
bonate, which blackens in presence of hydrogen sulphide.

3.  Sulphurous and Sulphuric Acids......The sulphide is shaken with

water coloured with a. drop of neutral litmus solution and, any decolorisa-
tion or reddening of the water noted.


cei4 -153-84

Colourless liquid of ethereal odour, ']) ••• •. 1-6, 7(1 -77", insoluble in
water, miscible in all proportions with alcohol or ether. It may be con-
taminated with chlorine, hydrochloric, acid, aldehydes, various organic
impurities and carbon bisulphide. The tests to be made are as follows :

1.  Volatility.-—25 c.c., evaporated on a, steam-bath, should leave no
appreciable, residue.

2.  Chlorine and Hydrochloric Acid.   -Sc-o Chloroform.

3.  Aldehydes.—-10 c.c. are shaken with 10 c.c. of potassium hydroxide
solution (i : 3) and heated for i minute :   the aqueous liquid should not

4.  Organic Impurities.—20 c.c. are shaken with 15 c.c. of pure cone.
sulphuric acid, which should not colour within an hour.

5.  Carbon Bisulphide.—10 c.c. are mixed with 10 c.c. of alcoholic
potassium hydroxide (i gram in 10 c.c. of absolute alcohol) ;   after an
hour, the liquid is faintly acidified with acetic acid and ;r 2 drops of dilute
copper sulphate solution added ; no browning or yellow precipitate (potas-
sium xanthate) should be produced within two hours.s much for collecting precipitates II and III—instead